In the age of energy shortage and environmentalism, solar energy has been an important substitute energy, and solar panels usually cooperate with high capacity batteries to achieve flexible solar energy application. Many public illumination devices are long time radiated by sunlight. If they are powered by solar energy, considerable electric power will be saved. In solar energy powered illumination devices, batteries store the electric energy, which is converted from solar energy, and timers turn on lamps using electric energy after sunset/turn off lamps to store electric energy after sunrise. Thereby, the solar energy powered illumination devices store energy during daytime and light up lamps at night regularly to make the best use of the environment-friendly energy. However, the abovementioned design has the intrinsic problem of solar energy. When the weather is unfavorable during daytime, solar panels absorb solar energy lower than the designed value, but the batteries still have to release energy to lamps at night. If there is a bad weather lasting for several successive days, the remaining battery capacity will persistently decrease, which may cause incapability of lighting lamps or interruption of lamp illumination and thus induce the problem of public security. Besides, the persistent low battery remaining capacity caused by a long-term bad weather will shorten the lifetime of batteries, which will obviously increase the repair and maintenance expense. At present, the conventional solar energy illumination devices still lack an effective solution for the abovementioned problems, which consumes budgets and impairs the popularization thereof.